Method and apparatus for the production of music



Oct. 31, 1933. B. F. MIESSNER 1,933,297

METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC Filed Oct. 12. 1932 a i /a g -fi FIOD. FILTIE AHR L5.

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Patented Oct. 31, 1933 PATENT OFFICE.

METHOD AND APPARATUS FOR THE PRO- DUCTION OF MUSIC Benjamin F. Miessner, Millburn Township, Es-

sex County, N. J., assignor to Miessner Inventions,,Inc., a corporation of New Jersey A Application October 12,

Claims.

This invention relates to musical instruments wherein the output sound is translated from electric oscillations, and more particularly to an improved selective source of such oscillations.

5 Instruments wherein the several notes in the pitch range are translated each from the oscillations of an individual mechanical oscillator, whether directly orthrough themedium of mechanico-electric and electroacoustic translations, have many advantages. At the same time relatively few mechanical oscillators fulfil the requirement for use therein that their upper partial vibrations be harmonically related to their fundamental vibrations. A form of oscillator which meets this requirement, but which for various mechanical reasons has been little employed in musical instruments, is-a bar or rod vibrated longitudinally; and it is an object of my invention to provide an improved musical instrument employing such bars as vibrators.

' It is a further object of my invention to provide ,an improved beat frequency musical instrument.

Other and allied objects will more fully appear from the following description and the appended claims.

In such description reference is to had to the accompanying drawing, of which:-

Figure 1 is acombined plan and schematic view of an embodiment of my invention;

Figure 2 is a partial cross-sectional view taken along the line 2-2 of Figure 1'; and

Figure 3 is a combined cross-sectional and schematic view illustrating a modification of a portion of the embodiment shown in Figures 1 and 2.

It is well known that the fundamental frequency of longitudinal vibrations of bars or rods, so long as any transverse dimension is reasonably small compared to the length, is dependent only on the length and material. For steel bars, for example, the fundamental frequency in cycles per second is approximately 100,000 divided by the length in inches. It may therefore be seen that longitudinally vibrated rods are most conveniently employed for the production of oscillations of a highfrequency. According to the present invention, a bar is employed for each note in the pitch range of the instrument; but instead of providing bars tuned to the respective frequencies of these notes, I provide a separate bar for each note, tuned to a frequency which is either the sum or difference of a single fixed frequency and the frequency of that note. The vibrations of these bars, which may be selectively produced 55 as hereinafter described, are translated intoelec- 1932. Serial No. 637,404

trio oscillations; these oscillations are caused to beat with those of anoscillator tuned to the fixed frequency above mentioned; and the difference frequencies produced as a result of such beating are translated into sound.

I may employ for example a fixed frequency of 25,000 cycles per second. The bar for each note will then be ground to a length suitable for the production of a frequency equal to 25,000 plus or minus the frequency of that note. While the fundamental frequencies of each of the individual bars may be either higher or lower than that of the fixed frequency oscillator, I shall hereinafter assume that the individual bars are tuned to fundamental frequencies higher than the fixed (0 frequency. Thus steel bars for the production of notes from 28 to 5,000 cycles may have lengths varying from approximately 4 inches downward to approximately 3% inches, and may produce oscillations of frequencies from 25,028 to 30,000 cycles per scond.

In Figures 1 and 2, I show a plurality of such bars 1. These have been illustrated asrigidly clamped at their respective centers to a relatively massive metal base 2, as by a strip 3 screwed at frequent points between the bars to a projection 4 on the base 2. It is'desirable that a minimum of surface of strip 3 and projection 4 contact with the bars. The clamping of the bars at their centers has certain advantages in respect of the vibrational characteristics of the bars, a bar so clamped always vibrating symmetrically about this point and thus eliminating the imposition of vibrational stress on the mounting. The requirement for rigidity of the latter is thereby materially lessened. At the same time I do not wish to imply a limitation of my invention to the employment of bars so supported; and it will be understood that I contemplate the use of longitudinally vibrated rods supported in any useful manner. I i

For selectively controlling the vibrations of the bars I have illustrated a hammer 5 arranged to strike the end of each bar, operated for example by depression of a key 6 through the medium of a conventional upright piano action, not shown. A damper 7 may normally rest on each bar 1, being raised therefrom upon depression of the associated key 6 in the manner of the dampers customarily employed in grand pianos. A bar 8 may pass under all the damper arms 9, thus being arranged to lift all the dampers upon depression of pedal 10, according to common piano practice. While I prefer the key actuated percussion method of selectively exciting damped vibrations 110 of the bars, it will be understood that the instru= ment may be played by direct percussion on the ends of the bars, without the key actuation, and that in turn a variety of non-percussion excitation methods, producing either damped or sustained vibrations, may be substituted in the practice of my invention.

For translating the vibrations of the bars into corresponding electric oscillations I have shown an electrostatic translation system operative at a free end of the bar, which will be understood to be a vibrational anti-node for all partial frequencies present in the vibration of the bar. Thus opposite the rear end of each bar in Figure 1 will be seen an electrically conductive screw 11, mounted in conductive member. 12 and therein rotatable to adjust the distance of its head from the end of the bar. Conductive member 12 may be insulatedly mounted to base 2 through the medium of insulation 13 and may be electrically connected to the grid of a thermionic vacuum tube 14. The cathode of tube 14 may be energized in any suitable manner; its anode current may be supplied as from a tap 15 on battery or other high voltage source 16; and its grid may be biased through high resistance 17 to a point maintained slightly more negative than the cathode by anode current flow through condensively by-passed resistance 18. Base 2, and therethrough bars 1, may be connected to the positive terminal of battery or source 16. Electrostatic shielding 50, connected to base 2, may advantageously be provided about the rear portions of bars 1, about the screws 11, and about tube 14 and its immediately associated apparatus.

Consideration being given to the manner of functioning of the translating system, it will be seen that between each bar 1 and the associated screw 11 a small electrostatic capacity exists.

' The total capacity made up of all these individual capacities in parallel is charged through resistance 1'1 to the potential of battery 16, but by virtue of the high value of resistance 1'1 this charge cannot change rapidly. Hence oscillatory variations of this capacity produced by vibration of any of the bars 1 will produce a corresponding oscillatory change in the voltage across the capacity. The oscillatory voltage component appears across resistance 17, is therefrom applied to the input of tube 14, and appears in amplified form in its output circuit, as will be understood.

While I have shown an electrostatic form of translation, I do not intend to limit my invention thereto, longitudinally vibrated bars adapting themselves readily to a variety of translation methods. A typical alternative is illustrated by the cross-section of a bar in Figure 3. Herein a bar 1 and its supports appear as in Figure 2. Freely surrounding the rear end of the bar may be provided a coil 19, of many turns of fine wire, mounted to base 2. A steady field may be maintained around this co l by a battery or other current source ,20 connected in series therewith. Oscillatory variation of this field by the vibration of the bar will produce corresponding oscillatory variations in the current in its circuit, which may be made available for use as through the medium of a transformer 21. If desired the battery 20 may be dispensed with, and the requisite steady field maintained by permanent magnetization of the bar 1.

Many other forms of translation may be mentioned', including magneto-electric pick-ups opposite the ends of the bars, piezo-electric pickups mounted to the ends of the bars, or bars themselves of piezo-electric material, etc., it being contemplated that any suitable translation method may be employed.

The electric output of the translating system may be led to the input of an electrical modulator 22, to the input of which may also be led the electric output of the fixed frequency oscillator above mentioned. This oscillator is indicated in Figure 1 as 23; and it will be understood that it may be of any form whatsoever, subject to the limitation that it provide an electric output which is of the proper fixed frequency and preferably rich in harmonics. Thus for example a simple vacuum tube oscillator may be employed; and there may be included in the oscillator, if desired, an overloaded stage of amplification for the fuller generation of harmonics by the oscillator system.

The harmonic output of the fixed frequency oscillator 23 may be regulated by a series of filters respectively tuned to its fundamental, second, third, fourth, etc., partials. These filters I have shown for example as series tuned circuits each comprising an inductance 24, a capacity 25 and a variable resstance 26, it being understood that the reactance of each filter is tuned to a different one of the partial frequencies of the oscillator. Reduction ,ofthe value of the variable resistance 26 in any of the filters will decrease the oscillator output at the partial frequency to which that filter is tuned, and vice versa.

In the modulator all the partials of the input from the fixed frequency oscillator 23 will beat with all the partials of the oscillations translated from any of the bars 1, such oscillation partials corresponding in general to the partial components present in the bar vibration. A great number of different frequencies will be present in the output oscillations from the modulator; but most of these will be of a very high frequency and may be removed by low-pass filter 27 connected in the modulator output and efilciently passing frequencies below a certain limit, which may be made some frequency between say 5,000 and 8,000 cycles. The significant output frequencies from the modulator will be the "difference" frequencies between the fundamentals of oscillator 23 and of a vibrated bar, between the second partial of oscillator 23 and that of a vibrated bar, between the third partial of oscillator 23 and that of a vibrated bar, etc. These d fference frequencies will of course form a harmonic series; and their relative strengths between different partials may be adjusted by varying the resistances 28 in the fixed oscillator output filters. Thus tone quality of the output sound may be adjusted.

The output oscillations from the modulator, after passing through filter 27, may be applied to potentiometer or volume control 28, operated for example by foot pedal 29, and thence through further amplifier 30 to loudspeaker or other electro-acoustic translating device 31 for translation into sound.

In the modulator 22 "difference frequencies transmissible by filter 2'7 will also be produced between oscillations translated from different bars simultaneously vibrating. These are similarand additive to the weak beat tones produced by the ear itself in listening to two notes simultaneously. In order to make these relatively weak compared to the desired "difi'erence frequencies above discussed, I prefer to make the average input to the modulator from the oscillator 23 of very large amplitude compared to that from the translating system. It will be understood, however, that there may be employed with my invention other means and systems already known in connection with beat frequency musical instruments for avoidance of these undesired difierence frequencies, such as grouping together of the individual oscillation sources for all the cs, the grouping together of the sources for all the cs, etc. and the use of twelve separate modulators, one for each of these groups.

Having thus described my invention in terms of certain embodiments thereof, and not intending any limitation of its scope by reason of such particular embodiments, I claim:

1. In a musical instrument wherein selectively produced electric oscillations of different frequencies are caused to beat with oscillations of fixed frequency, a selective source of different frequency oscillations comprising a plurality of tuned bars vibratable longitudinally, selective means controlling the longitudinal vibrations of such bars, and means for translating such vibrations into electric oscillations.

2. In a musical instrument, the combination of an oscillator yielding a fixed frequency electric output rich in harmonics; means for controlling the amplitudes of a plurality of the partial components of said output; a plurality of tuned bars vibratable longitudinally; means for translating longitudinal vibrations of said bars into electric oscillations; and means for beating said oscillations with said controlled oscillator output.

3. In a musical instrument, the combination of means for reducing electric oscillations of fixed frequency, means for controlling the harmonic structure of said oscillations, selective mechanical means for producing various frequency vibrations possessing harmonics, means for translating. said vibrations into electric oscillations, and means for beating said last mentioned with said first mentioned oscillations.

4. The method of producing music which includes producing electric oscillations of fixed frequency, controlling their harmonic structure, selectively producing various frequency mechanical vibrations possessing harmonics, translating said vibrations intov electric oscillations, and beating said last mentioned with said first mentioned oscillations.

5. In the operation of a beat frequency musical instrument, the method of suppressing undesired beats with relation to the desired beats, which includes beating together fixed frequency oscillations of high amplitude and selectively produced oscillations of a plurality of frequencies and of relatively low amplitude.

BENJAMIN F. MIESSNER.

CERTIFICATE OF CORRECTRON.

Patent No. 1,933, 297.

October 31, 1933.

BENJAMIN F. MIESSNER.

' It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Page 3, line 80, claim 3, for "reducing" read producing; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 3rd day of April, A. D. 1934.

(Seal) E. M. Hopkins Acting Commissioner of Patents. 

